Backlash compensator



p 29, 1942- v G. BRINKMANN 2,297,047

BACKLASH C OMPENSATOR Filed March 5, 1941 3 Sheets-Sheet 1 v jiiveiz/or Gag/5%? firznkmafliz Wa e/"22a s u/ P G. BRINKMANN Q 2,297,047

BACKLASI'L COMPENSATOR Filed March 5, 1941 3 Sheets-Sheet 2 Sept. 29, 1942. a. BRINKMANN BACKLASH COMPENSATOR s Sheets-Sheet 3 Filed March 3, 1941 III Guenp er Patented Sept. 29, 1942 BACKLASH COMPENSATOR Guenther Brinkmann, Detroit, Mich, assignor to Ex-Gell-O Corporation, Detroit, Mich., a corporation of Michigan Application March 3, 1941, Serial No. 381,443

11 Claims.

The present invention relates to improvements in automatic backlash compensators for mechanical drives. I

The primary object of the present invention is to provide a novel automatic backlash compensator which is operable to impart a predetermined movement to a mechanical drive for a machine element upon reversal of the drive, the movement being of an amount and in a direction to compensate or offset the efiect of the backlash in the drive.

Another object is to provide a new and improved automatic backlash compensator which is readily adjustable to vary the amount of movement imparted to the drive, and which may be rendered functionally inefiective at will.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings,

Figure 1 is a fragmentary elevational view of a machine tool including the backlash compensator embodying the features of my invention.

Fig. 2 is a fragmentary vertical. sectional view of the machine.

Fig. 2 is a cross sectional View taken along line 2=*2 of Fig. 2.

Fig. 3 is a side elevational view of the backlash compensator, partially in vertical section substantially along line 33 of Fig. 1.

Fig. 4 is a vertical sectional view of the compensator taken along line 44 of Fig. 3.

Fig. 5 is a diagrammatic representation of the electric circuits for controlling the compensator.

Referring more particularly to the drawings,

the backlash compensator, constituting the present embodiment of the invention, may be utilized in various types of mechanical drives for machine elements, and for purposes of illustration is shown as employed in a thread grinding machine. This machine comprises a base I supporting a reciprocatory slide 2. A spindle 3 is suitably journaled in a headstock 4 on the slide 2 and is adapted to support a work blank A. The spindle 3 is rotated and translated axially in timed relation relative to a grinding wheel (not shown) to grind on the work blank A a thread of a predetermined lead.

A screw shaft 5 is suitably journaled in the slide 2 against relative axial movement and extends in the direction of reciprocation of the slide. One end of the screw shaft 5 is suitably connected for rotary drive to a reversible electric motor 6. The spindle 3 is connected through a train of gears 1 to the screw shaft 5 so that the two will rotate in positive timed relation.

To provide means for translating'the slide 2 and, therefore, the spindle 3 vintimed relation to the rotation of the spindle, a master lead screw 8 is fixed on the screw shaft 5 and is in thread engagement with a nut 9 normally anchored in fixed position on the base I. In the present instance, the nut 9 is rigidly secured coaxially within a hollow cylindrical supporting member [0 which is secured in a fixed axial position for rotation within a housing II on the base I. Connected to the housing II is a gear housing I2 having a circular space I3 about the lead screw 8, and formed with an elongated bearing sleeve I4 having a bore l5 opening tangentially to the space. A worm wheel I6 is rigidly connected to one end of the supporting member [0 for rotation therewith within the space I3, and meshes with a worm I1 on the inner end of an adjusting shaft I8 journaled in and extending through the bearing sleeve I4. A hand wheel I9 is keyed. to the outer end of the shaft l8 for rotation therewith and is secured in position by a suitable clamp nut 20. It will be seen that when the adjusting shaft I8 is not rotated, the worm l1, through engagement with the worm wheel I6 will lock the nut 9 against rotation. Consequently, rotation of the lead screw 8 through coaction with the nut 9 will effect translation of the spindle 3 in timed relation to the spindle rotation and in a direction determined by the direction of drive from the electric motor 6.

Upon reversal of thelead screw 8, any backlash between th screw and the nut 9 and also in the train of gears I would normally disturb the phase relationship between the spindle rotation and translation. An automatic backlash compensator is provided for adjusting the nut 9 upon each reversal of the lead screw 8'to compensate for this backlash so that th thread lead defined by the rotation and translation of the spindle will remain accurately in phase in both directions of translation.

The backlash compensator in its preferred form comprises a tubular shaft 2| rotatably supported in the bore l5 and projecting from the forward end thereof. Two plain tubular bushings 22 and 23 ar tightly fitted in opposite ends of the shaft 2| and support the adjusting shaft I8. The innermost bushing 23 has an external peripheral end flange 24 disposed between the inner end of the tubular shaft 2| and the contiguous end of the worm IT. The outer end of the tubular shaft 2| has a reduced portion 25 defining a shoulder 26. A seal 21 is positioned about the reduced shaft portion 25 against the shoulder 26, and a plate 28 encircles the shaft portion externally of the seal and is secured to the outer end of the bearing sleeve M to confine the tubular shaft 2| in axial position. Splined to the outer end of the reduced shaft portion 25 for rotation therewith is a compensator wheel 29 confined in position between the hand wheel 19 and th plate 28. Consequently, the worm H, the clamp nut 20 and the plate 28 serve to maintain the various parts in assembled relation with the bearing sleeve l4.

Suitable means is provided for connecting the hand wheel I9 and the compensator. wheel. 29..

The supply of fluid under pressure to the cylinder 50 is under the control of a direction valve 55 supported on a plate 56 on the base I. In the present instance, the valve 55 has a casing 51 with port connections to the lines 5| and 52 and also to a pressure supply line 58 and an exhaust hne 59. A valve piston 60 is reciprocable in the casing 51 and projects from opposite ends thereof.

To provide suitable means for automatically reversing the direction valve 55 in timed relation to reversal of the rotary drive to the spindle.3 and the lead screw 8, two solenoids 6| and for joint rotation or for disconnecting'th'em" so hand wheel l9. A plunger 32 i reciprocable in;

the bore 3| and has a detent pin 33 adapted "for engagement with any one ofa plurality Of holes 34 in the rim of. the compensator wheel2'9. The

plunger 32 is. urged towardjthe wheel. 29"by a' coiled compression spring 35 seated in the. bore 31, and is provided on the outer end with a hand knob 36'whereby the. pin 33 may be withdrawn fromjthe selected holei34'; vTwo complemental projections 3 1and'38 are formed respectively on. the adjacent ends of the sleeve 30. and hand knob 36, and are movable selectively either. into interfitti'ng. engagement to release the. pin.33 forengagement with the hole 34-, or; into endabutting; engagement to lock the. pin inretracted position.

Rigid with the bearing'sl'eeve I 4 .is a perpendicular sleeve 39. having. a. longitudinal bore 40 intersecting one side of the bor 15. Plain tu bular bushingsfil and 42 are fitted in opp site ends of'the bore 40, and one endiof the latter is closed bya cap 43"; A plunger 44. extends into the'other 'endf .offlthe bore 40 and is guided for reciprocationby the bushings; 41 and 42. The; plunger 44 is fo 'med in one sidewith a longitudinal; gear; rack 45 which meshes with a gear of. the: valve.

62 are mounted on the plate 56 at opposite ends These-solenoids have plungers 63 and? respectively which are pivotally connected attheir: outer ends to the alined arms of two bellcrank. levers 65 and 66 mounted on the plate 56'; The other arms of the bell crank levers 65 andIGfiLeXtend laterally into position respectively for engagementwithopposite ends of the valve piston 60. The solnoids'filiand'GZhave exciting.

circuits 61 and 68- adapted to be connected in parallel respectively with theelectric circuits 691and 10 for. energizing the electric motor 6 for. operation in reverse directions.

v In operation, uponexcitation of the solenoid- 6|, the plunger 63 will.actuate the bell crank lever- 65; to shi ftzthe valve piston 60 'into one end.

lead screw 8 and in the train of gear-$ 1.. Uponenergization. of the solenoid fiz' theplunger 64 will shift the valve. piston fin into'its otherend position, thereby connecting the pressure line 58 to the line 52'and. the line 5| toithe-iexhaust' line 46 formedjin the periphery of the tubular" shaft 2L. It'wi'll be seen that when the hand Wheel I9 and thecompensator wheel 29' are connected, reciprocationxof' the. plunger .44 will effect rotatiOll'QfflthB nut 9to adjust the axial position of the ma; screw 8, and therethrough the axial position of the spindle 3 relative to the position of rotation; I

The outer end of the plunger 44 is connected through a floating coupling 4''! to a piston rod 48; A piston 49 on the rod'48 is reciprocable in a cylin'der 50 rigidly mounted on the basel. -A suitable motive fluid, such for example as air under'pressure, is adapted to be supplied alter-' natelythrough lines or flow passages 5| and 52 to opposite ends of the cylinder 50 so as to reciprocat the piston 49. The extent of'movement is limited'at one end by engagement of" the piston 49 with oneend wallof the cylinder 59, and is limited at the other end by a screw 53 adjustably threaded throngh the cap 43 for end engagement by-theplunger 44. It will be seen that the-screw 53 affords means for adjusting the extent of movement of theplungr 44 so that the compensating movement imparted to the nut 9 may be accurately correlated to the amount of backlash; When no backlash compensation is desired the adjusting screw 53 may be turned down to confine the piston 49 against one end of the cylinder 50. A lock nut 54 onthe adjusting screw 53 is adapted to be turned against the cap 43 to secure the screw in position of adjustment.

59. As' a result, the plunger 44 will :be' moved into its oppositeend position so as to impart a predetermined rotary movement to the nut 91the same in amount as before but in the; opposite direction. Sincethe excitation of tlie solenoids GI and 62 iscontrolled in accordance-wilth'the direction of operation o f the motor 6, backlash is compensated for automaticallyupon'each reversal of the spindle 3. By retracting the detent pin 33; the drive connection between the plunger 44 and the nut 9 may beinterrupted so t hat 'the hand wheel l9 may be operated manually to effect any desired independent 'adjustmentof the nut, Such. adjustment mayb e resorted to on occasion to effect lead pick-upbetween the work blank A and the grinding wheel' I claim as my invention: l i

1. A backlash compensatorcofnp'rising, in combination with a rotary axially movable screw element and means for reversibly rotating said element, an axially stationaryscr'ew threaded element in threaded engagement with said first mentioned element, and means for automatically rotating said last mentionedielement fa predetertent upon reversal of rotation of said lead screw.

3. A backlash compensator comprising, in com bination with a rotary axially movable lead screw and means for reversibly rotating said lead screw, an axially stationary nut in threaded engagement with said lead screw, and means normally locking said nut against rotation and being automatically operable to rotate said nut a predetermined extent upon reversal of rotation of said lead screw.

4. A backlash compensator comprising, in combination with a rotary axially movable lead screw and means for reversibly rotating said'lead screw, an axially stationary nut in threaded engagement with said lead screw, means including a shaft for rotatably adjusting said nut, a plunger reciprocable transversely of said shaft and geared to said shaft to rotate the latter in timed relation to its reciprocation, and means for automatically reciprocating said plunger through a predetermined extent in opposite directions respectively upon reversal of rotation of said lead screw in opposite directions.

5. A backlash compensator comprising, in combination with a rotary axially movable lead screw and means for reversibly rotating said lead screw, an axially stationary nut in threaded engagement with said lead screw, means including a reciprocatory member movable transversely of said nut to rotate said nut, adjustable means for determining the extent of reciprocation of said member, and a fluid motor operable to move said member into one end position upon reversal of rotation of said lead screw in one direction and to move said member into the other end position upon reversal of rotation of said lead screw in the other direction.

6. A backlash compensator comprising, in combination with a base, a support reciprocable on said base in a rectilinear direction, a spindle journaled on said support and extending in said direction, a lead screw rotatably anchored to said support for movement therewith and extending in said direction, gear means interconnecting said spindle and said lead screw for timed rotation, and reversible drive means for rotating said spindle and lead screw, a nut rotatably anchored on said base in threaded engagement with said lead screw, a worm wheel coaxially fixed on said nut, a shaft journaled in said base and having a worm meshing with said worm wheel, a coaxial shaft, releasable means interconnecting said shafts for joint rotation, and means for automatically rotating said coaxial shaft a predetermined extent in opposite directions respectively upon reversal of said drive means to rotate said lead screw in opposite directions, whereby to rotate said nut to an amount and in a direction to compensate for backlash between said lead screw and said nut and in said gearing.

'7. A backlash compensator, comprising, in combination with a base, a support reciprocable on said base in a rectilinear direction, a spindle journaled on said support and extending in said direction, a first screw element, rotatably anchored to said support for movement therewith and extending in said direction, gear means interconnecting said spindle and said screw element for timed rotation, and reversible drive means for rotating said spindle and screw element, a second screw element rotatably anchored on said base and in threaded engagement with said first screw element, a worm wheel coaxially fixed on said second screw element, a shaft journaled in said base transversely of said screw elements and. having a worm meshing with said worm wheel, a coaxial shaft, means interconnecting said shafts for joint rotation, and means for automatically rotating said coaxial shaft an adjustable predetermined extent in opposite directions respectively upon reversal of said drive means to rotate said first screw element in opposite directions, whereby to rotate said second screw element to an amount and in a direction to compensate for backlash between said first and second screw elements.

8. A backlash compensator comprising, in combination with a rotary axially movable first screw element and means for reversibly rotating said element, an axially stationary second screw element in threaded engagement with said first screw element, two concentric shafts mounted for rotation transversely of said second screw element, a worm on one of said shafts and meshing with a worm wheel coaxially fixed on said second screw element, a hand wheel fixed on said one shaft, a compensator wheel fixed on the other of said shafts, releasable means for engaging and disengaging said wheels, a gear on said other shaft, a reciprocatory plunger mounted for movement transversely of said other shaft and having a longitudinal gear rack meshing with said gear, means for adjustably limiting the extent of movement of said plunger in one direction, a fluid motor for reciprocating said plunger and for limiting the extent of movement of said plunger inthe other direction, a source of fluid under pressure, a reversing valve for connecting said source alternately to opposite sides of said motor, and means for reversing said valve automatically upon reversal of the rotation of said first screw element, whereby to impart to said second screw element a predetermined rotation.

9. A backlash compensator comprising, in combination with a rotary axially movable first screw element and means for reversibly rotating said element, an axially stationary second screw element in threaded engagement with said first screw element, two concentric shafts mounted for rotation transversely of said second screw element, a worm on one of said shafts and meshing with a worm wheel coaxially fixed on said second screw element, a hand wheel fixed on said one shaft, a compensator wheel fixed on the other of said shafts, releasable means for engaging and disengaging said wheels, a gear on said other shaft, a reciprocatory plunger mounted for movement transversely of said other shaft and having a longitudinal gear rack meshing with said gear, means for adjustably limiting the extent of movement of said plunger, a fluid motor for reciprocating said plunger and for limiting the extent of movement of said plunger in the other direction, a source of fluid under pressure, a reversing valve for connecting said source alternately to opposite sides of said motor, and means for reversing said valve.

10. A backlash compensator comprising, in combination with a base, a slide on said base reciprocable in a predetermined direction, a lead screw anchored for axial movement with said slide, and means for reversibly rotating said lead screw, 'a housing mounted in fixed position on said base, a cylindrical member mounted for rotary adjustment in said housing, a nut secured coaxially to said member and in threaded engagement with said lead screw, a worm wheel fixed coaxially on said member, a gear housing rigid with said first mentioned housing and having a bearing sleeve opening tangentially to said worm wheel and a second bearing sleeve transversely intersecting'i said first mentioned; bearing sleevei,a. tubulan'shia'ftjournaledin said first mentioned; sleeve and;- having; a peripheral: gear, a shaft; journaled; in said: tubular shaft, a: worm on;v said: last mentionedgshaft and; meshing with said worm; wheeh. releasable means interconnecting'said shafts: for-j joint rotation, a plungerreciprocableirr said second; sleeve'and having a longitudinal geanrack meshing with'said gear,

and means-'for-reversibly shifting said plunger 2. 10;

predetermined extent.

111,A- backlash rcompensator comprising, in

combination with a,v base, 'a'slide; on said basereciprocable a predetermined direction, a lead screw anchored for axial movement with said slide, and. meansfor reversibly rotating said lead screw, a housing mountedin fixed position on said-base, a nut; mounted for rotary adjustment:

in said housing and; in threaded engagement with saidlead screw, a worm Wheel fixed coaxially on said nut, a gear housing enclosing said worm wheel and having a bearing sleeve open- 5, ing tangentially to said worm wheel and a second bearing sleeve transversely intersecting said first mentioned bearing sleeve, a tubular shaft journaled in said first mentioned sleeve and having a peripheral gear, a shaft journaled in said tubular shaft, a worm on said last mentioned shaft and meshing with said worm wheel, means interconnecting said shafts for joint rotation, a plunger reciprocable in said second sleeve and having a longitudinal gear rack meshing with r said gear, and means for reversibly shifting said plunger a predetermined extent.

GUENTHER BRINKMANN. 

